Techniques for vibrationally isolating electronic devices have been extensively described. For example, in U.S. Pat. No. 1,907,986 (1933) to Little a piezo-electric crystal holding device is employed to prevent interference with frequency characteristics. The crystal is mounted inside a frame with a silk chord placed within a plane that has a particular relationship with orientations of the faces of the crystal and with the touch points of the chord selected to be at nodal points for minimum impact on the performance on the crystal. A spring loaded device is described in the U.S. Pat. No. 2,688,059 to Holzinger.
In the U.S. Pat. No. 3,046,423 to Wolfskill et al a vibration resistant mounting for a piezo-electric crystal is described. The mounting uses wire members, which are preferably resonant to the frequency of the crystal or some multiple or submultiple thereof. A spring type mounting for a wafer shaped piezo-electric device is described in the U.S. Pat. No. 3,069,572 to Dick et al. In U.S. Pat. No. 3,937,991 to Massa et al. a bilaminar crystal plate is supported within a frame structure by resilient pads attached to the nodal points of the crystal. An anti shock and vibration mounting is described in U.S. Pat. No. 4,404,459 to Harton.
A foam mounting for an oscillator is shown and described in U.S. Pat. No. 4,479,096 to Fowks. In U.S. Pat. No. 4,502,022 to Stahl vibration and shock resistance for an oscillator is obtained by suspending the oscillator from a wire. In U.S. Pat. No. 4,677,397 to Nakayama et al an oscillator element is mounted on a resonant leaf spring. In U.S. Pat. No. 4,899,076 a tubular piezo-electric element is elastically supported by a torsionally displacing support within a vacuum inside a casing. In U.S. Pat. No. 5,218,510 to Bradford an electrostatic sensitive package is suspended between opposing films, capable of discharging a static charge, and peripherally suspended between opposing parts of a package to protect against damage from electrostatic discharges and physical abuse.
Crystal oscillators are required to deliver a pure sine wave for optimum performance. In practice their performance is influenced by factors such as temperature and vibrations. Vibrations typically induce undesirable sidebands, called phase noise, and it is important to be able to reduce phase noise to very low levels for maximum effectiveness. For example, an oscillator mounted on a typical prior art vibration isolation mounting may exhibit a sensitivity to vibrations by producing side bands near the center frequency of the oscillator within 130 db or less of the peak oscillator signal. Conventional vibration resistant mountings typically exhibit sideband spikes because of resonances or other mounting characteristics and are also sensitive to high physical displacements at low vibrational frequencies.